WASHINGTON, Feb 20 (Reuters) - U.S. Vice President Joe Biden told Ukrainian President Viktor Yanukovich in a phone call on Thursday that the United States is prepared to sanction officials responsible for violence against civilian protesters in Kiev, the White House said.

"He called upon President Yanukovich to immediately pull back all security forces - police, snipers, military and paramilitary units, and irregular forces," the White House said in a statement.

"The Vice President made clear that the United States is prepared to sanction those officials responsible for the violence," the White House said. (Reporting by Roberta Rampton; Editing by Peter Cooney)